The present invention relates to generating a reference voltage, and more particularly, to a reference voltage generator having at least one bipolar junction transistor biased by a negative base voltage and an associated reference voltage generating method.
Voltage references have a major impact on the performance and accuracy of signal processing circuits. For example, a bandgap reference circuit is widely used in a variety of applications for providing a temperature independent voltage. Low voltage operation is an important design issue in mobile devices, because of demanding for low power consumption. Hence, when the bandgap reference circuit is used by a mobile device for supplying a reference voltage to signal processing circuits of the mobile device, the bandgap reference circuit is required to operate normally under a low power supply condition. However, as the semiconductor process technologies are developing to reduce the line widths, the maximum allowable supply voltage is scaled down accordingly. Usually, the conventional bandgap reference circuit relies on base-emitter voltages of bipolar junction transistors for generating the temperature independent voltage. Hence, the supply voltage of the conventional bandgap reference circuit is mainly constrained by the base-emitter voltage (e.g., 0.7V). As a result, the conventional bandgap reference circuit is not applicable to certain applications with lower supply voltages.